Not that I realistically expect you to switch to a different language, but there's a major flaw in the English language that has the potential to lead to online discussions degenerating. And it would be a hell of a hard time to fix it.
The problem is that it doesn't have any representation of tone-of-voice in text.
It may seem obvious to ask someone to "be nicer" but the writer can't predict how the reader will respond. A common half-solution is for the writer to say what they don't mean but that produces clutter, becomes boring, and it is impossible to anticipate every potential interpretation.
The important thing is to assume good intent. Except in the case of targeted swearing (and targeted swearing only), by which I mean aimed at a forum member. And as tempting as it is to swear back, that's only going to make it worse.
No, smilies are not the solution. It's okay to use them but they aren't intended as serious indications of someone's mood.
Failing to think of a better solution, I propose using text colours for this purpose. (Not a perfect solution as it won't work in monochrome or plain text, and some colours (e.g. red and green) have to be mutually exclusive if you don't want to confuse colourblind people, but better than nothing, I suppose.) You don't have to adopt this system but I suggest at least trying to improve the quality of online discussion.
My choice of representations (coloured or otherwise)???
Black (default) - normal (none of the listed examples)
Yellow (#AF8F00) - joyful
Deep blue (#0000BF) - sad/depressed
Light blue (#4080BF) - dreamy
Teal (#408080) - tired
Purple (#8000BF) - embarassed
Brown (#806040) - frustrated
Grey (#606060) - disappointed
RED (#BF0000) IN ALL CAPS - angry (you probably shouldn't actually use this one, but I provided it just in case)
Red (#BF0000) in bold - warning
ALL CAPITALS - shouting (a pre-existing convention; you should not use it for emphasis)
Small text - whispering
(I will still allow green (#008000)/red (#BF0000) for good/bad, or any colour regardless of its meaning here when referring to colour-coded objects (e.g. wiring).)
If you have any other ideas, feel free to tell me about them. (Some of the colours above are deliberately darkened from their "usual" versions, as maximum brightness on the red and especially green channels would make them difficult to read.)
I don't recommend switching to a different font to convey a different meaning. Notably, I can't stand cursive handwriting, which is sometimes barely recognisable. (There's no tool to select a different font here, anyway...)
EDIT: Just figured out a catchy name for it - Rainbow Mood Encoding System (R.M.E.S.).
